GNU /ɡnuː/ is a Unix-like computer operating system developed by the GNU Project. It is composed wholly of free software. It is based on the GNU Hurd kernel and is intended to be a "complete Unix-compatible software system" GNU is a recursive acronym for "GNU's Not Unix!", chosen because GNU's design is Unix-like, but differs from Unix by being free software and containing no Unix code.

Debian GNU/Hurd console startup and login

Development of GNU was initiated by Richard Stallman in 1983 and was the original focus of the Free Software Foundation (FSF), but no stable release of GNU yet exists as of October 2014. However, non-GNU kernels, most famously the Linux kernel, can also be used with GNU software. The combination of GNU software and the Linux kernel is known as Linux or GNU/Linux. (see GNU/Linux naming controversy)

Stallman views GNU as a "technical means to a social end."

History

Richard Stallman, founder of the GNU project

The plan for the GNU ("GNU's Not Unix!") operating system was publicly announced on September 27, 1983, on the net.unix-wizards and net.usoft newsgroups by Richard Stallman. Software development began on January 5, 1984, when Stallman quit his job at the Massachusetts Institute of Technology (MIT) Artificial Intelligence Laboratory so that they could not claim ownership or interfere with distributing GNU as free software. Richard Stallman chose the name by using various plays on words, including the song The Gnu.(00:45:30)

The goal was to bring a wholly free software operating system into existence. Stallman wanted computer users to be "free", as most were in the 1960s and 1970s – free to study the source code of the software they use, free to share the software with other people, free to modify the behavior of the software, and free to publish their modified versions of the software. This philosophy was later published as the GNU Manifesto in March 1985.

Richard Stallman's experience with the Incompatible Timesharing System (ITS), an early operating system written in assembly language that became obsolete due to discontinuation of PDP-10, the computer architecture for which ITS was written, led to a decision that a portable system was necessary.(00:40:52) It was thus decided that GNU would be mostly compatible with Unix. At the time, Unix was already a popular proprietary operating system. The design of Unix was modular, so it could be reimplemented piece by piece.

Much of the needed software had to be written from scratch, but existing compatible third-party free software components were also used such as the TeXtypesetting system, the X Window System, and the Mach microkernel that forms the basis of the GNU Mach core of GNU Hurd (the official kernel of GNU). With the exception of the aforementioned third-party components, most of GNU has been written by volunteers of the GNU Project; some in their spare time, some paid by companies, educational institutions, and other non-profit organizations. In October 1985, Stallman set up the Free Software Foundation (FSF). In the late 1980s and 1990s, the FSF hired software developers to write the software needed for GNU.

As GNU gained prominence, interested businesses began contributing to development or selling GNU software and technical support. The most prominent and successful of these was Cygnus Solutions, now part of Red Hat.

Components

The system's basic components include the GNU Compiler Collection (GCC), the GNU C library (glibc), and GNU Core Utilities (coreutils), but also the GNU Debugger (GDB), GNU Binary Utilities (binutils), the bash shell and the GNOME desktop environment. GNU developers have contributed Linux ports of GNU applications and utilities, which are now also widely used on other operating systems such as BSD variants, Solaris and Mac OS X.

Many GNU programs have been ported to other operating systems, including proprietary platforms such as Microsoft Windows and Mac OS X. Compared to their proprietary Unix counterparts, GNU programs have also been shown to be more reliable.

As of August 2014, there are a total of 452 GNU packages (including decommissioned, 373 excluding) hosted on the official GNU development site.

gNewSense, an example of a FSF approved distribution

Parabola, an example of a FSF approved distribution that uses a rolling release model

GNU variants

The official kernel of GNU Project is the GNU Hurd microkernel; however, as of 2012, Linux is officially part of the GNU Project in the form of Linux-libre, a variant of Linux with all proprietary components removed.

Other kernels like the FreeBSD kernel also work together with GNU software to form a working operating system. The FSF maintains that Linux, when used with GNU tools and utilities, should be considered a variant of GNU, and promotes the term GNU/Linux for such systems (leading to the GNU/Linux naming controversy). The GNU Project has endorsed variants using Linux, such as gNewSense, Trisquel and Parabola GNU/Linux-libre. Other GNU variants which do not use the Hurd as a kernel include Debian GNU/kFreeBSD and Debian GNU/NetBSD from Debian brings to fruition the early plan of GNU on a BSD kernel.

Copyright, GNU licenses and stewardship

The GNU Project recommends that contributors assign the copyright for GNU packages to the Free Software Foundation, though the Free Software Foundation considers it acceptable to release small changes to an existing project to the public domain. However, this is not required; package maintainers may retain copyright to the GNU packages they maintain, though since only the copyright holder may enforce the license used (such as the GNU GPL), the copyright holder in this case enforces it rather than the Free Software Foundation.

For the software developed under the GNU Project, Stallman wrote a license called the GNU General Public License (first called Emacs General Public License), with the goal to guarantee users freedom to share and change free software. Stallman wrote this license after his experience with James Gosling and a program called UniPress, over a controversy around software code use in the GNU Emacs program. For most of the 80s, each GNU package had its own license: the Emacs General Public License, the GCC General Public License, etc. In 1989, FSF published a single license they could use for all their software, and which could be used by non-GNU projects: the GNU General Public License (GPL).

This license is now used by most GNU programs, as well as a large number of free software programs that are not part of the GNU Project; it is also the most commonly used free software license. It gives all recipients of a program the right to run, copy, modify and distribute it, while forbidding them from imposing further restrictions on any copies they distribute. This idea is often referred to as copyleft.

In 1991, the GNU Lesser General Public License (LGPL), then known as the Library General Public License, was written for the GNU C Library to allow it to be linked with proprietary software. 1991 also saw the release of version 2 of the GNU GPL. The GNU Free Documentation License (FDL), for documentation, followed in 2000. The GPL and LGPL were revised to version 3 in 2007, adding clauses to protect users against hardware restrictions that prevent user to run modified software on their own devices.

In addition to GNU's own packages, the GNU Project's licenses are also used by many unrelated projects, such as the Linux, which is often used with GNU software. A minority of the software used by GNU, such as the X Window System, is licensed under permissive free software licenses.

Logo

GNU_30th_logo

The logo for GNU is a gnu head. Originally drawn by Etienne Suvasa, a bolder and simpler version designed by Aurelio Heckert is now preferred. It appears in GNU software and in printed and electronic documentation for the GNU Project, and is also used in Free Software Foundation materials.